Reverse water gas shift reaction using supported ionic liquid phase catalysts

• Published in: Applied catalysis. B, Environmental Vol. 232; pp. 299 - 305
• Main Authors: Yasuda, Tomohiro, Uchiage, Eriko, Fujitani, Tadahiro, Tominaga, Ken-ichi, Nishida, Mayumi
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 15.09.2018; Elsevier BV
• Subjects: Activation energy; Catalysis; Catalysts; Catalytic activity; Catalytic cycle; Constitution; Diffuse reflectance spectroscopy; Electrolytes; Fourier transforms; Infrared analysis; Ionic liquid; Ionic liquids; Ionization; Mass spectrometry; Mass spectroscopy; Mass transport; Phase transitions; Protonation; Reverse water gas shift reaction; Ru catalyst; Ruthenium trichloride; Shift reaction; Silica; Silica gel; Silicon dioxide; Solvation; Supported ionic liquid phase; Surface area; Water gas; Reverse water gas shift reaction; Ru catalyst; Supported ionic liquid phase; Ionic liquid; Catalytic cycle
• ISSN: 0926-3373; 1873-3883
• DOI: 10.1016/j.apcatb.2018.03.057

[Display omitted] •Both surface area and solvation of catalyst by ionic liquid affect catalytic activity of SILP catalyst.•SILP catalyst exhibits greater catalytic activity for RWGSR comparing with conventional homogeneous system.•Rate determining step of RWGSR using SILP catalyst is different from that in homogeneous system.•Silica support may facilitate protonation process in catalytic cycle of RWGSR using SILP catalyst.•20 cycles was achieved in cycle test of RWGSR using SILP-Cl (1.6). The reverse water–gas shift reaction (RWGSR) using a supported ionic liquid-phase (SILP) catalyst consisting of Ru catalyst, ionic liquid (1-butyl-3-methylimidazolium chloride ([C4mim]Cl)), and porous silica gel support, was investigated. The catalytic activity of the SILP catalyst toward RWGSR strongly depends on the kind of Ru catalyst and amount of IL. Among the three kinds of Ru catalysts ([RuCl2(CO)3]2, Ru3(CO)12, and RuCl3), [RuCl2(CO)3]2 exhibits the best catalytic activity. Brunauer–Emmett–Teller (BET) surface area analysis and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) analyses of the SILP catalyst based on [RuCl2(CO)3]2 and [C4mim]Cl revealed that both the solvation of the active catalytic Ru species and the surface area of the ionic liquid phase strongly affect catalytic activity. Hence, these factors help to determine the optimum amount of [C4mim]Cl in the SILP catalyst. The resulting SILP catalyst, with an optimum constitution, exhibited greater catalytic activity than the homogeneous system in which the same amounts of [RuCl2(CO)3]2 and [C4mim]Cl were employed. Catalytically active Ru species during RWGSR in both systems were investigated by means of electrospray ionization-mass spectrometry (ESI-MS). Interestingly, the rate-determining step in the two systems was different, implying that the silica support lowers the activation energy of the protonation reaction in the catalytic cycle. Therefore, the facilitation of the RWGSR by a SILP catalyst system can be realized by good mass transport, derived from the large surface area, as well as the effect of the silica support on activation energy. Furthermore, 20 cycles of the RWGSR using the SILP catalyst were accomplished.